Wick structure of heat pipe

ABSTRACT

A wick structure of a heat pipe includes a wick structure attached to an internal wall of a tubular member. The tubular member is fabricated from metal material with good conductive characteristics, and the wick member is formed of a mesh structure and a plurality of particulate members. The mesh structure is in the form of a ring attached to an internal wall of the tubular member, and the particulate members are embedded in the interstices of the mesh structure. The wick structure is attached to the internal wall of the tubular member by sintering, such that a wick structure with a villiform structure is formed. Thereby, the peeling or fracture tendency of the wick structure during the mechanical process of the heat pipe avoided. In addition, the axial rod used for the sintering process is not required, such that the cost is greatly reduced.

BACKGROUND OF THE INVENTION

The present invention relates in general to a wick structure of a heatpipe, and more particularly, to a wick structure fabricated by a processduring which the peeling and fracture tendency of the wick structure iseliminated, while the heat absorption and the conduction of the wickstructure is greatly enhanced.

FIGS. 1 and 2 illustrate a conventional wick structure of a heat pipe.FIG. 1 shows a heat pipe having a tubular member 10 a and a screen mesh20 a, and FIG. 2 shows a heat pipe including a sintered heat pipe havingthe tubular member 10 a and a sintered material 30 a. The wick structureformed of the mesh 20 a and the sintered material 30 a serves as amedium for liquid flow induction. The mesh-type heat pipe winds thescreen mesh 20 a around an axial rod to be inserted into the tubularmember 10 a. When screen mesh 20 a is attached to the internal wall ofthe tubular member 10 a be the insertion of the axial rod, the axial rodis removed from the tubular member 10 a to form the mesh-type heat pipe.The sinter-type heat pipe uses an axial rod 31 a inserted into thetubular member 10 a. Powder-like sintered material 30 a is then pouredinto the tubular member 10 a. The tubular member 10 a is cooled downafter sintering process, and the axial rod 31 a is removed from thetubular member 10 a to form a sinter-type heat pipe. In application, theheat pipes are configured according to specific structures of heatdissipation devices or heat sources. For example, the heat pipes may beconfigured with an L shape or a U shape, or configured into a flat tubeor a tube having higher section and lower section, such that the heatpipes can be properly connected to the heat dissipation fins or heatsource.

However, the above heat pipe wick structure suffers from the followingdisadvantages during fabrication or mechanical processes.

Firstly, the tubular member 10 a and the screen mesh 20 a are fabricatedfrom different types of materials. When the heat pipe is forced to bend,the corners of the screen mesh 20 a are stretched to reduce thestructure density thereof. The screen mesh 20 a may also peel from theinternal wall of the tubular member 10 a during the bending process.Thereby, the capillary force of the screen mesh 20 a is reduced.

Secondly, the bending step frequently causes fracture of the sinteredmaterial 30 a. In addition, as the axial rod 31 a has to be insertedinto and removed from one end of the tubular member 10 a, the insertionand removal of the axial rod 31 a inevitably removes a portion of thesintered material 30 a. Further, as the removal step is performed afterthe tubular member 10 is softened by an annealing process, the tubularmember 10 a is easily deformed by the removal process.

Thirdly, it is not easy to position the axial rod 31 a at the axis ofthe tubular member 10 a during thermal fusion or condensation, such thatuneven thickness of the wick structure is resulted.

Fourthly, when a heat pipe with a large gauge is fabricated, the volumeand mass of the axial rod 31 a are consequently increased. Therefore,longer time is consumed for heating and cooling to cause more variationsof the wick structure.

To resolve the problems caused by the conventional heat pipe asdescribed above, with many years of experience in this field, a wickstructure of a heat pipe has been developed as described as follows.

BRIEF SUMMARY OF THE INVENTION

The present invention provides a wick structure of a heat pipe. Acomposite structure is formed to prevent the wick structure from beingpeeling or fractured during mechanical process performed on the heatpipe. Thereby, the heat absorption and conduction capability of the heatpipe is enhanced. Further, the axial rod used in sintering is notrequired any more. Therefore, the fabrication process is simplified, andthe cost is reduced.

The wick structure provided by the present invention includes a wickstructure attached to an internal wall of a tubular member. The tubularmember is preferably fabricated from metal material with good conductingperformance, and the wick structure includes a mesh member and aplurality of particulate members. The mesh member is in the form of anelongate circular ring attached to the internal wall of the tubularmember, and the particulate members are embedded in the interstices ofthe mesh member. The wick structure is attached to the internal wall bysintering, such that a dense wick structure is formed.

These and other objectives of the present invention will become obviousto those of ordinary skill in the art after reading the followingdetailed description of preferred embodiments.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary, and are intended toprovide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

These as well as other features of the present invention will becomemore apparent upon reference to the drawings therein:

FIG. 1 shows a conventional heat pipe;

FIG. 2 shows another type of conventional heat pipe;

FIG. 3 shows a cross sectional view of a heat pipe in one embodiment ofthe present invention;

FIG. 4 shows a local enlargement of FIG. 3; and

FIG. 5 shows a cross sectional view of a heat pipe in another embodimentof the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to the preferred embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings. Wherever possible, the same reference numbers are used in thedrawings and the description to refer to the same or like parts.

Referring now to the drawings wherein the showings are for purpose ofillustrating preferred embodiments of the present invention only, andnot for purposes of limiting the same, FIG. 3 and FIG. 4 show a heatpipe in one embodiment of the present invention. As shown, the heat pipeincludes a tubular member 10 and a wick structure 20.

The tubular member 10 is preferably fabricated from material such ascopper that has good conducting characteristics. The tubular member 10may be formed with various geometric cross sections. In this embodiment,the tubular member 10 has a circular cross section. The tubular member10 has an open end 11, a close end 12, and an internal wall 13.

The wick structure 20 has a fusion (melting) point lower than that ofthe tubular member 10 to advantage the sintering process performed onthe wick structure 20. The wick structure 20 comprises a mesh 21 and aplurality of particulate members 22. The mesh 21 includes a woven mesh,porous thin plate or thin film with a plurality of porosities and anuneven surface with a plurality of recesses and protrusions. In thisembodiment, the mesh 21 includes a woven mesh having a circular ringcross section. The perimeter of the woven mesh is slightly larger thanan internal perimeter of the tubular member 10, such that mesh 21 can befirmly attached to the internal wall 13 of the tubular member 10. Oneend (front end) of the mesh 21 extends towards a bottom surface of theclose end 12 of the tubular member 10 to improve the thermal conductionof the tubular member 10. The particulate members 22 include metalpowders or fine broken fibers. In this embodiment, metal powders areused as the particulate members 22. The dimensions of the particulatemembers 22 are substantially smaller than the dimensions of theinterstices of the mesh 21, such that the particulate members 22 can beembedded in the interstices of the mesh 21. The fusion point of theparticulate members 22 is lower than that of the mesh 21, such that theparticulates members 22 can be easily embedded in the mesh 21 during thesintering process, and a dense wick structure can be formed.

To attach the wick structure 20 to the tubular member 10, the mesh 21 isinserted in the tubular member 10 from the open end 12 thereof. Theparticulate members 22 are then poured into the tubular member 10. Thetubular member 10 is then evenly rotated to evenly distribute theparticulate members 22 in the mesh 21. A sintering process is performedto attach the particulate members 22 and the mesh 21 to the internalwall 13 of the tubular member 10.

FIG. 5 shows a cross sectional view of a heat pipe in another embodimentof the present invention. In this embodiment, a support member 14 isdisposed in the tubular member 10 after the wick structure 20 is formedin the tubular member 10. The support member 14 has a fusion pointhigher than that of the mesh 21 and the particulate members 22. Thesupport member 14 can be in the form of a linear or plate spiralstructure or an elastic plate curled as a roll. By the elastic forceexerted from itself, the mesh 21 and the particulate members 22 arepressed against the internal wall 13 of the tubular member 10.Therefore, the mesh 21 will not shrink or curl during sintering process,and the wick structure 20 can be firmly attached to the internal wall13.

Accordingly, the present invention has at least the followingadvantages:

The composite wick structure prevents the wick structure from peeling orbeing fractured during sintering or mechanical process.

The mesh and the particulate members are attached to the tubular memberby sintering, such that the wick structure can be fabricated fromcomposite materials. Therefore, there are more choices and lesslimitation in design and fabrication.

During the fabrication process, the axial rod used for the conventionalheat pipe is not required. Therefore, the cost is reduced, and thequality is improved. In addition, the uneven thickness of the wickstructure is avoided.

This disclosure provides exemplary embodiments of wick structure of aheat pipe. The scope of this disclosure is not limited by theseexemplary embodiments. Numerous variations, whether explicitly providedfor by the specification or implied by the specification, such asvariations in shape, structure, dimension, type of material ormanufacturing process may be implemented by one of skill in the art inview of this disclosure.

1. A wick structure to be attached to an internal wall of a tubularmember, comprising a mesh in the form of an elongate circular ring and aplurality of particulates embedded in interstices of the mesh, whereinthe mesh and the particulates embedded therein are attached to theinternal wall of the tubular member by a sintering process.
 2. Thestructure of claim 1, wherein the tubular member is fabricated from agood thermal conductive metal material.
 3. The structure of claim 1,wherein the mesh includes a woven mesh.
 4. The structure of claim 1,wherein the tubular member includes an open end and a close end, and themesh extends towards an internal bottom surface of the close end.
 5. Thestructure of claim 1, wherein the tubular member has a fusion pointhigher than that of the wick structure.
 6. The structure of claim 5,wherein the mesh is fabricated from a thin layer with a plurality ofporosities.
 7. The structure of claim 6, wherein the thin layer includesa plurality of recesses and protrusions.
 8. The structure of claim 1,wherein the particulates have a fusion point lower than that of themesh.
 9. The structure of claim 1, wherein the particulates includemetal powders.
 10. The structure of claim 1, wherein the particulatesinclude a plurality of fine broken fibers.
 11. The structure of claim 1,further comprising a support member disposed in the tubular member topress the wick structure against the internal wall of the tubularmember.
 12. The structure of claim 10, wherein the support member has afusion point higher than those of the mesh and the particulates.
 13. Thestructure of claim 10, wherein the support member includes a platespiral structure.
 14. The structure of claim 10, wherein the supportmember includes a linear spiral structure.
 15. The structure of claim10, wherein the support member includes a porous plate curled as a roll.16. The structure of claim 10, wherein the support member is fabricatedfrom a resilient material.